Modern global radiomap-based positioning technologies are based on generating large global databases containing information on cellular and/or non-cellular signals receivable from radio nodes such as base stations or access points at a plurality of positions. The information may originate entirely or partially from users of these positioning technologies acting as data collectors (so-called “crowd-sourcing” of information collection).
The data provided by these data collectors is typically in the form of “fingerprints”, which at least contain information on measurements taken from the data collector's cellular and/or non-cellular radio interfaces at a position of the data collector. A fingerprint may further contain the data collector's position that is measured or estimated based on, e.g., received satellite signals of a global navigation satellite system (GNSS). Alternatively, the position of the data collector may be determined and associated with the fingerprint by another entity, e.g. a server. In the case of measurements on cellular signals, the results of the measurements may contain a system-wide and/or local identification of the cellular communication system cells observed, their signal strengths and/or pathlosses and/or timing measurements like timing advance (TA) or round-trip time (RTT). For measurements on wireless local area network (WLAN) signals, as an example of signals of a non-cellular network, the results of the measurements may contain a basic service set identification (BSSID), like the medium access control (MAC) address of observed access points, and/or the service set identifier (SSID) of the observed access points, and/or the signal strength of received signals (received signal strength indication RSSI or physical Rx level in dBm with a reference value of 1 mW, etc.), and/or pathloss measurements/estimates and/or timing measurements (like e.g. RTT).
This fingerprint information may then be transferred to a server or cloud, where the data (usually from a multitude of users) may be collected and where a radiomap for positioning purposes may be generated and/or updated based on the data. Such a radiomap can for instance comprise estimates for respective coverage areas of one or more radio nodes and/or radio channel models for these one or more radio nodes.
In the end, this radiomap may be used for estimating the position of mobile devices. This may function in two modes. The first mode is the device-assisted mode, in which the mobile device performs the measurements of the cellular and/or non-cellular air interface, provides the measurements to the remote server, which in turn, based on the radiomap, determines and provides the position back to the mobile device. The second mode is the device-based mode, in which the mobile device has a local copy of the radiomap (or only a subset of the global radiomap). This subset copy is downloaded by the mobile device from a remote server for the area of interest (e.g. a small area around the current location, for a whole country, or so). This subset copy can of course also be pre-installed to the mobile device in the factory, but may then need to be refreshed at some point.